Demo Event reporting is not yet available. It is expected to be released in early September. Once it's been released, you'll be able to report attendance for any Demo Events you've held. The information you'll be reporting will include the following:
– Full name of the professor who ran the Demo Event
– That professor's player ID
– Total number of attendees
– Player IDs for any attendees, if they have a player ID
If you have further questions, they should be directed to TPCi Customer Support at https://www.pokemon.com/uk/customer-service.